While it is known in the prior art to use various fungi in the preparation of sheet-like paper products, as exemplified by U.S. Pat. No. 2,811,442, which discloses the use of mycelium from various natural fungi, such as mushroom and aquatic fungi, in paper sheet manufacture, and U.S. Pat. No. 2,026,253, disclosing the preparation of transparent or semi-transparent sheet material from paper mill slimes, the only apparent recognition of the utility of fungal mycelia or yeast in relation to filtration is disclosed in French Pat. No. 2,151,814. In this latter patent, cotton is soaked in a milk solution containing green kaolin and a minor amount of powdered yeast and thereafter dried, cut and rolled into the form of a cigarette filter.
There has been no appreciation in the prior art, however, of the present discovery that improved filters can be prepared using as the filter media yeast or fungal mycelia when in particulate form. Furthermore, there has been no recognition of the filtration efficiency of such filters, particularly in relation to the removal of particulate matter from gaseous streams, such as tobacco smoke.